Method of producing alloys



March 15, 1932. P. H. BRACE METHOD OF PRODUCING ALLOYS Filed Feb. 27, 1928 7'0 Vacuum Pump.

INVENTOR Porter hiBrace.

Patented Mar. 15, 1932 UNITED STATES PATENT OFFICE,

PORTER H. BRACE, F WILKINSBURG, PENNSYLVANIA, ASSIGNOR T0 WESTINGHOUSE ELECTRIC &; MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA METHOD OF PRODUCING- ALLOYS Application filed February 27, 1928. Serial No. 257,145.

My invention, relates to alloys and more particularly to alloys containing silicon as one of the principal ingredients.

An object of my invention is to provide alloys and especially iron-silicon alloys, that are comparatively free from carbon and other non-metallic impurities.

Another object of my invention is to provide-a method of preparing ferrous alloys, and especially iron-silicon alloys, under reducing or non-oxidizing conditions.

. A further object of my invention is toprovide a method of preparing silicon alloys,

and especially silicon steel, which consists cs sentially in passing vaporized elements, such as, silicon or silicon compounds, through a bed of heated iron in fragmentary form, or in the molten condition, under non-oxidizing or reducing conditions.

In producing siliconalloys for instance, silicon steel, it has heretofore can the practice to melt the iron and then to add silicon or an iron-silicon alloy of high silicon content,

such as ferro-silicon, to produce a silicon steel. This practice, however, has not been entirely V satisfactory because ferro-silicon and commercially pure silicon are electric furnace pro ducts and contain anappreciable quantity of carbon. 7

I have made the discovery that when silicon of a fairly high degree of purity, say about 95%, and the metal with which an alloy is desired are heated under reduced pressure to a temperature slightly below the melting point of the metal, the silicon will vaporize and will be readily absorbed by the metal.

CAD

The same results may also be obtained by maintaining the metal or alloy to which it is desired to add silicon in the molten condition and passing vapors of a volatile silicon compound, such as a silicon hydride or a silicon halide, or amixture of two or more of these compounds, through the molten metal. Hydrogen, hydrogeneous or other reducing gases, such as carbon monoxide, methane or other hydrocarbons or a mixture of'two or more of such gases may be added to the var porized silicon, or if preferred, a neutral gas such as nitrogen may be utilized.

The temperature at which the metal is maintained will, of course, be dependent upon the volatile silicon compounds employed and upon the metal or metals with which an alloy is desired. In producing silicon alloys it is essential, however, that the temperature be sufiiciently high to dissociate or reduce the silicon-compound to silicon.

My improved process will be better understood by reading the specification in conjunction with the accompanying drawings in which:

Figure-l is a vertical cross sectional view of an induction furnace, illustrating means for practicing my invention as applied to the production of silicon alloys when the metal with which an alloy is desired is in the solid state; and

Fig. 2 is a similar view, illustrating means for practicing my invention when the metal with which the alloy is desired is in the molten state.

Referrin to Fig. 1 of the drawings, the induction furnace comprises a supporting frame 2 provided with bearings 33 to receive trunnions H carried by the furnace and providing means by which the furnace may be used for any purpose such as discharging its contents.

The furnace proper comprises a cylindrical shell or casing 5, a crucible 6 and an inductor coil 7 disposed circumferentially around the crucible 6. The crucible 6 may be of any material such as zirconium silicate. The inductor coil 7 comprises a plurality of turns of a conductor and is provided with a plurality of terminal posts 8, 9 and 10 which are connected to the uppermost, lowermost and intermediate coils respectively. The inductor coil employed in the furnace in which my process is practiced may be made hollow 40 shown in through in order to keep the material of 5 which'the coil is made at a safe operating temperature.

The intervening space between the crucible 6 and the casing 5 may be filled with a suitable pulverized material, such as zirconium silicate. An annular ring 11, ofi'set at its innermost portion, constitutes the top of the casing, the offset portions providing a seat for a cover made of a suitable refractory material 12 which has an opening at its central portion for'purposes to be hereinafter described. I

The furnace so far described is somewhat similar to furnaces disclosed in the copending applications of R. B. Lincoln, Serial No. 176,885, filed March 21, 1927, and Porter H. Brace, Serial No. 125,155, filed July 27, 1926, both of which are assigned to the Westinghouse Electric and ManufacturingCompany. As will be observed by reference to these cases, the furnaces disclosed may or may not be provided with iron cores in their magnetic circuits. Furnaces of such type, which are operable to produce the melting of current conducting material, at low frequencies of the order of 25 to 350 cycles per second,are particularly adapted for use inmy improved process although it will be understood that any suitable furnace may be employed,

At the lower portion of the furnace, 1 provide a chamber 13 havin a gas supply pipe 14 leading into the chamier and bein separated from the crucible 6- by aflper orated diaphragm 21. I

In practicing my invention, in the furnace Figure 1 of the drawings, commercially pure silicon is .placed'inthe chamber 13 and metal in scrap. 'or' fragmentary form is introducedinto the. crucible '6. A par-.

tial vacuum is maintained-in-the furnace and when the silicon and metal are heated almost to the melting point of the metal, the silicon will have a higher vapor tension than the carbon, or other nonmetallic impurities associated with it and its vapor will pass upward through the perforated diaphragm 21 and b readily absorbed by the metal. a

In making silicon-iron alloys by this process, for example, the silicon and iron are heated to a temerature of approximately 1400 C. At thlstemperature, the vapor tension of silicon ishigher than that of most of the elements associated with it, and this is particularly true of carbon, so that by dis-- tilling silicon vapors into a bed of hot electrolytic iron, a means is provided for producing a silicon-iron alloy of a very high degree of purity under conditions suitable for preventing oxidation or the absorption of oxygen by' the resultant drogen or hydrogen bearing gasessuch as alloy. If desired, hyr methane may be passed through the pipe 14, chamber 13 and crucible 6 in order to preserve a reducing atmosphere.

The alloy, having been formed in the solid state, may then be melted by suitable means in an atmosphere of a volatile compound of silicon such as silicon chloride, silicon hydri'de, silicon fluoride or other halogen or mixed halogen and hydrogen compounds of silicon, or, if preferred, a mixture of the vapors of such compounds with hydrogen or halogens, such as chlorine or fluorine may be employed.

Figure 2 of the drawings illustrates the manner of practicing my invention when the process 1s applied to producing an alloy of sillcon when the metal or alloy to which the silicon is to be added is in the molten form.

The metal or alloy is introduced into the crucible 6 either in the molten form or, if desired, it may be melted in the furnace. Vapors of a volatile silicon compound such as the hydrides or halogen compounds of silicon, are then passed into the chamber 13 and through the openings 21 up through the molten metal which is maintained at a sufficient temperature to dissociate the silicon compound forming the desired silicon alloy, the halogen or hydrogen being removed as a gas, or as gaseous compoundsof iron or other basic material that may e present.

It is sometimes desirab e to add a reducing Q I g s, such as hydrogen, or a hydrogen bearirk gas to the silicon vapors of the volatile silicon compound and ass the mixture through the molten meta the-silicon compound being either dissociated by the heat of the metal or reduced by the hydrogen so that the silicon thus obtained willbe absorbed by the molten metal. When hydrogen or other reducing gases are added to the volatilesilicon compounds, the hydrogen and vaporous silicon com ound are passed into a mixer 22'from a suitable source of supply through pipes 14 and 20, respectively. They are intimately associated together in the mixer and are passed through the pipe 22 into chamber 13 and are then drawn through the molten metal.

By using my improved process, I am enabled to producea SlllCOIl' alloy, and particularly silicon steel, in a high state of purity and this is especially true with respect to carbon which has a' deleterious effect on the magnetic properties of the steel.

My process is also adaptable for forming alloys of iron or other metals with volatile utilizing the 5 above that aeaaerc metals, such as magnesium or aluminum. By volatile chlorides of titanium, vanadium or chromium, I may also produce alloys of iron or other metals free from carbon or oxygen with these elements, in which case the alloys may be melted in an atmosphere of the chloride or other volatile compounds of these metals. The particular type of furnace utilized is also not of vital importance as any suitable furnace may be employed in which a partial vacuum can be maintained.

I, therefore, desire that only such limitations be placed upon my invention as are required by the prior art and the appended claims.

I claim as my invention:

1. The process ofproducing silicon alloys which comprises heating a metal or an alloy in a furnace to its melting point and passing a vapor containing silicon and a reducing gas through the molten metal while maintaining a partial vacuum in said furnace.

2. The process of forming silicon alloys which'comprises maintaining a metal or alloy in a molten condition in a suitable furnace and passing vapors containing a volatile silicon compound and a reducing gas throu h the molten metal while maintaining a partlal vacuum in said furnace.

3. The process of producing an iron-silicon alloy which comprises maintaining iron in a molten state in a suitable furnace, and passing a vapor containing a silicon compound and a reducing gas through the molten metal while maintaining a partial vacuum in said furnace.

4. The process of producing an iron-silicon alloy which comprises maintaining iron in a molten state in a suitable furnace, and passing a vapor containing a silicon compound and hydrogen through the molten metal while maintaining a partial vacuum in said furnace.

5. The process of producing iron-silicon alloys in a high state of purity which comprises melting iron in a Suitable furnace, passing a vapor containing silicon through the molten metal from a separate vessel having passages leading into the furnace and maintaining the pressure in the furnace below atmospheric pressure but at a pressure above that at which substantial-amounts of impurities in the silicon will volatilize.

6. The process of producing iron-silicon alloys in a high state of purity which comprises placing iron in a suitable furnace, heating it to a temperature slightly below its melting point and passing a vapor containing silicon through the metal from a separate vessel having passages leading into the furnace and maintaining a pressure in the furnace below atmospheric but at a pressure at which substantial amounts of impurities. in the silicon will vaporize.

( PORTER H. BRAOE. 

